1. Field of the Invention
The present invention relates generally to network management systems, and more specifically is directed toward management of network resources using distributed intelligence and state management.
2. Related Art
Telecommunication service providers (e.g., MCI Telecommunications Corporation) provide a wide range of services to their customers. These services range from the transport of a standard 64 kbit/s voice channel (i.e., DS0 channel) or subrate thereof to the transport of higher rate digital data services (e.g., video). Both voice channels and digital data services are transported over the network via a hierarchy of digital signal transport levels. For example, in a conventional digital signal hierarchy 24 DS0 channels are mapped into a DS1 channel. In turn, 28 DS1 channels are mapped into a DS3 channel.
Routing of these DS1 and DS3 channels within a node of the network is generally performed by crossconnect functions. Multiplexing and transmission of channels between nodes is typically provided via fiber-optic transmission systems. Fiberoptic transmission systems can multiplex a plurality of DSn channels into a higher rate transmission over a single pair of fibers. In one example, signal formats for the fiber-optic transmission systems are defined by the manufacturer. These proprietary systems are referred to as asynchronous transmission systems.
Alternatively, a fiber-optic transmission system can implement the synchronous optical network (SONET) standard or the counterpart synchronous digital hierarchy (SDH) standard. The SONET standard defines a synchronous transport signal (STS) frame structure that includes overhead bytes and a synchronous payload envelope (SPE). One or more channels (e.g., DS1 and DS3 channels) can be mapped into a SPE. For example, a single DS3 channel can be mapped into a single STS-1 frame. Alternatively, 28 DS1 channels can be mapped into virtual tributaries (VTs) within a single STS-1 frame.
Various STS-1 frames can be concatenated to produce higher rate SONET signals. For example, a STS-12 signal includes 12 STS-1 frames, while a STS-48 signal includes 48 STS-1 frames. Finally, after an STS signal is converted from electrical to optical, it is known as an optical carrier (OC) signal (e.g., OC-12 and OC-48).
An end-to-end path of a provisioned channel within a network typically traverses a plurality of nodes. This provisioned channel is carried over transmission facilities that operate at various rates in the digital signal hierarchy. For example, a provisioned DS1 channel may exist as part of a DS3, VT1.5, STS-1, STS-12, OC-12, and OC-48 signal along parts of the end-to-end path. This results due to the multiplexing and demultiplexing functions at each of the nodes.
One of the goals of a network management system is to monitor the performance of the provisioned channel. Performance of the provisioned channel can include various measures. One measure is the unavailability of the provisioned channel. Unavailability is generally defined as the amount (or fraction) of time that a channel is not operational. Various causes such as cable cuts can lead to channel downtime. Network responses to channel downtime can include automatic protection switching or various restoration procedures (e.g., digital cross-connect distributed restoration).
Although unavailability is a major performance measure from a customer's standpoint, other performance measures can also be critical. For example, if a customer desires a digital data service for the transmission of financial data, the number of errored seconds or severely errored seconds may be a concern.
One of the most fundamental challenges facing network management systems is the identification of an accurate representation of the condition (or state) of the network. In particular, the network management system is concerned with the state of the physical hardware contained in the network elements under its supervision. The state of the physical hardware is used to infer the state of logical network services which the network elements provide.
More specifically, network management systems rely on the centralized reception, filtering, and correlation of alarms and performance information from the network elements. In one example, the individual network elements combine to forward several million alarm/performance messages to the network management system for subsequent analysis. To reduce the amount of processing required, the centralized network management application may provide a filtering function that can correlate alarms, thereby reducing the number of alarm messages from several million to possibly several hundred thousands. After this filtering function is performed, the alarm/performance information is analyzed to identify root causes of the alarms and determine the associated condition of the network. As one can readily appreciate, this solution to network management is time consuming, processing resource intensive, and unscalable.